What factors affect electrochemical cells?

1 Answer
Ernest Z. · Dr. Hayek
Feb 11, 2014

The Gibbs free energy change determines the voltage of an electrochemical cell. This in turn depends on factors such as concentration, gas pressure, and temperature.

Explanation:

Gibbs Free Energy

The Gibbs free energy measures how far a system is from equilibrium.

It therefore determines the voltage (driving force) of an electrochemical cell.

#ΔG = -nFE# or #E = -(ΔG)/(nF)#

where #n# is the number of moles of electrons transferred and #F# is the Faraday Constant.

Concentration and Gas Pressure

#ΔG = ΔG° - RTlnQ#, where #Q# is the reaction quotient.

For an equilibrium reaction such as #"A" ⇌ "B + C"#,

#Q =(["B"]["C"])/(["A"])# or #Q = (P_"B" P_"C")/P_"A"# if the substances are gases.

#E# depends on #ΔG#, #ΔG# depends on #Q#, and #Q# depends on concentration and pressure.

Therefore both concentration and gas pressure affect the voltage of the cell.

Temperature

According to the Nernst Equation,

#E = E° - ((RT)/(nF))lnQ#

The temperature term in this equation shows that temperature also affects the cell voltage.

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